On a winter day in 1569, Dirk Willems faced a moment of decision. He had just escaped from prison, where he was facing torture and death for belonging to a persecuted religious minority. Willems fled across an ice-covered pond in Asperen, Holland, with his stronger and heavier jailer close behind. Then, suddenly, his jailer fell through the ice. Unable to climb out, he pleaded for help to escape the icy waters.

With his freedom in front of him, Willems acted with ultimate selflessness: He turned back and rescued his pursuer. The jailer, following his orders, took Willems back to prison where, a few weeks later, he was burned alive. For his martyrdom, present-day Asperen has named a street in honor of its folk hero (Toews, 2004).

What drives people to feel and act so heartlessly toward those, like Willems, who differ from them? What motivates the selflessness of the responses of so many who have died trying to save others?

What leads us to like or even love another? Do birds of a feather flock together—or do opposites attract? Does absence make the heart grow fonder—or does out of sight more often mean out of mind? Do good looks attract us—or does a good personality matter more?

As such questions demonstrate, we are social animals. We may assume the worst or the best in others. We may approach them with closed fists or open arms. But as the novelist Herman Melville remarked, “We cannot live for ourselves alone. Our lives are connected by a thousand invisible threads.” In this chapter, we explore some of these connections and see how social psychologists study them.